JP3596026B2 - Method for producing catalyst for purifying exhaust gas of engine - Google Patents

Method for producing catalyst for purifying exhaust gas of engine Download PDF

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JP3596026B2
JP3596026B2 JP8790994A JP8790994A JP3596026B2 JP 3596026 B2 JP3596026 B2 JP 3596026B2 JP 8790994 A JP8790994 A JP 8790994A JP 8790994 A JP8790994 A JP 8790994A JP 3596026 B2 JP3596026 B2 JP 3596026B2
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catalyst
exhaust gas
adsorbent
engine
adsorbent powder
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JPH07148429A (en
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敏嗣 上岡
啓司 山田
康人 渡辺
智士 市川
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Mazda Motor Corp
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Mazda Motor Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
    • F01N2240/18—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being an adsorber or absorber
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/12—Hydrocarbons

Description

【０００１】
【産業上の利用分野】
この発明は、三元触媒（ＴＷＣ）にＨＣ吸着剤を担持させて、エンジンの排気ポートから排出されるＨＣ（炭化水素）、ＣＯ（一酸化炭素）、ＮＯｘ（窒素酸化物）の有害ガスを浄化するようなエンジンの排気ガス浄化用触媒の製造方法に関する。
【０００２】
【従来の技術】
従来、エンジンの排気ガス浄化用触媒としては、例えば、特開平３−２０２１５４号公報に記載の触媒がある。
すなわち、図５に示すように、コージエライト（cordierite、化学記号Ｍｇ２Ａｌ４Ｓｉ５Ｏ１８）等のハニカム状の触媒成分担持用担体１０１(いわゆるハニカム担体)の表面に、Ｐｔ−Ｒｈ系触媒成分（白金・ロジウム系触媒成分）を含むアルミナ層（詳しくはγ−Ａｌ２Ｏ３層）からなる第１コート層１０２を設け、この第１コート層１０２の上に、ＣｅＯ２（酸化セリウム）とエンジンの未燃焼ガス成分を吸着するＨＣ吸着剤とを含む第２コート層１０３を設けた排気ガス浄化用触媒１０４である。
【０００３】
この従来の排気ガス浄化用触媒１０４によれば、ハニカム担体１０１の多数の細孔１０５…を排気ガスが流通する際に、排気ガス低温時には同排気ガス中のＨＣ（Hydrocarbon 、ハイドロカーボン）は第２コート層１０３内のＨＣ吸着剤に吸着され、排気ガス温度が高まった時、ＨＣ吸着剤からＨＣが脱離され、第１コート層１０２内に拡散して浄化され、浄化率を高めることができる利点がある反面、Ｐｔ−Ｒｈ系触媒金属の第１コート層１０２がＨＣ吸着剤を含む第２コート層１０３の内側に形成されている関係上、脱離ＨＣと触媒金属との充分な接触が得られず、良好なＨＣ浄化率の向上を図ることができない問題点があった。
【０００４】
【発明が解決しようとする課題】
この発明は、ＨＣを吸着するＨＣ吸着剤から脱離して放出されるＨＣを触媒金属と接触しやすい構造とすることで、ＨＣ浄化率の充分な向上を図ることができ、しかも、ＨＣ吸着剤粉末の表面に薄く触媒金属が配設された触媒金属担持ＨＣ吸着剤粉末を、触媒成分担持用担体にウオッシュコートすることで、ＨＣが脱離して放出される時、ＨＣ吸着剤粉末表面の触媒金属で放出ＨＣを燃焼除去し、ＨＣ浄化率の充分な向上を図ることができ、さらに、ウオッシュコートの層にセリウムを含む水溶液を含浸し、焼成することによりＣeＯ２（酸化セリウム）からのＯ２（酸素）の供給により、酸化反応にてＨＣを燃焼除去して、ＨＣ浄化率のさらなる向上を図ることができるエンジンの排気ガス浄化用触媒の製造方法の提供を目的とする。
【０００５】
【課題を解決するための手段】
この発明によるエンジンの排気ガス浄化用触媒の製造方法は、触媒成分担持用担体の表面にＨＣを吸着するＨＣ吸着剤粉末が分散して配置され、上記ＨＣ吸着剤粉末の少なくとも外側に未浄化の排気ガス成分を浄化する触媒金属が分散配置されたエンジンの排気ガス浄化用触媒の製造方法であって、ＨＣを吸着するＨＣ吸着剤粉末と、未浄化の排気ガス成分を浄化する触媒金属を含む溶液とを混合した後、蒸発乾固して上記ＨＣ吸着剤粉末の表面に上記触媒金属を担持して、触媒金属を担持したＨＣ吸着剤粉末を形成した後に、触媒金属担持ＨＣ吸着剤粉末を触媒成分担持用担体の表面にウオッシュコートし、さらに該ウオッシュコートの層にセリウムを含む水溶液を含浸し、焼成したものである。
【０００６】
【発明の効果】
この発明によれば、ＨＣ吸着剤粉末の少なくとも外側に触媒金属が分散配置された構造であるから、ＨＣ吸着剤から脱離して放出されるＨＣは必ず触媒金属と接触するので、ＨＣ浄化率の充分な向上を図ることができる効果がある。しかも、蒸発乾固定により、ＨＣ吸着剤粉末の表面に薄く触媒金属が担持された触媒金属担持ＨＣ吸着剤粉末を、触媒成分担持用担体にウオッシュコートする方法であるから、ＨＣが脱離して放出される時、ＨＣ吸着剤粉末表面の触媒金属で放出ＨＣを燃焼除去して、ＨＣ浄化率の充分な向上を図ることができる効果がある。
【０００７】
さらに、ウオッシュコートの層にセリウムを含む水溶液を含浸し、焼成（焼成することにより酸化セリウムとなる）する方法であるから、ＣｅＯ２（酸化セリウム）からのＯ２（酸素）の供給により、酸化反応にてＨＣを燃焼除去して、ＨＣ浄化率のさらなる向上を図ることができる効果がある。
【０００８】
【実施例】
この発明の一実施例を以下図面に基づいて詳述する。
図面はエンジンの排気ガス浄化用触媒の製造方法を示すが、まず図１〜図３を参照して排気ガス浄化装置の構成について説明する。図１において、エンジンの排気系に介設される排気ガス浄化装置１は、車両のアンダフロア位置に配設されると共に、この排気ガス浄化装置１は前後両端に接合フランジ部２，３を備え、排気ガス入口４にコーン部５を介してキャタリストケース６の前端側を接続し、このキャタリストケース６の後端側はコーン部７を介して排気ガス出口８に接続している。ここで、上述の排気ガス入口４は排気通路を介してエンジンの排気ポートに連通され、上述の排気ガス出口８は排気通路を介してマフラに連通接続される。
【０００９】
上述のキャタリストケース６内の排気上流側となる前段には未浄化の排気ガス成分を浄化する三元触媒９を配設し、排気下流側となる後段にはＨＣを吸着するＨＣ吸着剤、未浄化の排気ガス成分を浄化する三元触媒、ＣｅＯ２（酸化セリウム）が複合された複合触媒１０を配設している。
【００１０】
上述の後段側の複合触媒１０は、図２に示すように、その外径が円柱状で、かつ軸方向の形状がハニカム状に形成され、多数の細孔１１…を有する。しかも、その断面構造は図３に示すように、コージエライト（Ｍｇ２Ａｌ４Ｓｉ５Ｏ１８）製ハニカム担体１２（触媒成分担持用担体のこと）の表面に、ＨＣを吸着するＭＦＩ（ゼオライ）粉末からなるＨＣ吸着剤粉末を含有する第１コート層１３を形成し、この第１コート層１３の外表面にＰｄ（パラジウム）等の触媒金属を含有する第２コート層１４を形成し、さらに上述の第１コート層１３と第２コート層１４との２層コートハニカムに対してセリウムを含浸手段により担持させている。
【００１１】
このように、ＨＣ吸着剤粉末（第１コート層１３参照）の外側に未浄化の排気ガス成分を浄化する触媒金属（第２コート層１４参照）が分散配置された構造であるから、排気ガス中のＨＣはＨＣ吸着剤にトラップされた後に、このＨＣ吸着剤から脱離するが、この放出ＨＣは必ず触媒金属の層（第２コート層１４参照）と接触するので、ＨＣ浄化率の充分に向上を図ることができる効果がある。
【００１２】
上述の図３に示す複合触媒１０の製造方法を、図４に示す工程図に基づいて詳述する。
まず図４の第１工程Ｓ２１で、ＨＣ吸着剤粉末と触媒金属含有水溶液（この実施例では水溶液を用いるが、水溶液に代えて有機溶液を用いてもよい）とを混合する。
【００１３】
すなわち、ＨＣ吸着剤として水素イオン交換ＭＯＲ（モルデナイト）粉末（ケイバン比２０）を２００ｇ用い、触媒金属含有水溶液として硝酸パラジウム水溶液（Ｐｄ、４．４ｗｔ％）を１２０ｇ用い、これら両者を１００ｇのＨ２Ｏ（水）中で混合撹拌する。
【００１４】
次に図４の第２工程Ｓ２２で、加熱手段として例えばホットプレートを用いて上記水溶液を加熱しつつ撹拌を続けると、ＨＣ吸着剤粉末の上にＰｄ（パラジウム）が担持された乾燥粉末を得ることができる。この方法を一般に蒸発乾固という。
【００１５】
次に図４の第３工程Ｓ２３で、上述の触媒金属担持ＨＣ吸着剤粉末をハニカム担体にウオッシュコートする。すなわち、上述の蒸発乾固手段により得られた触媒金属担持ＨＣ吸着剤粉末と、バインダとしての水和アルミナとを重量比で５：１の割合にて水と混合して、スラリーを形成し、このスラリーに対してハニカム担体を浸漬、引上げ、エアブラスト、乾燥を繰返すことで、ハニカム担体にＰｄ担持ＭＯＲをウオッシュコートした後に、焼成する。なお、総担持量は２００ｇ／リッタとした。
【００１６】
次に図４の第４工程Ｓ２４で、上述のウオッシュコート済みのハニカム担体に対してセリウムを含浸させる。すなわち、Ｃｅ（ＮＯ３）３（硝酸セリウム）１６４ｇを１リッタの水に溶解し、この硝酸セリウム水溶液を用いて上述のハニカム担体に含浸させ、次に図４の第５工程Ｓ２５で、Ｃｅ（ＮＯ３）３（硝酸セリウム）水溶液含浸後のハニカム担体を焼成して、ＣｅＯ２（酸化セリウム）を５０ｇ／リッタ担持させた複合触媒を製造した。
【００１７】
このように、上記実施例のエンジンの排気ガス浄化用触媒の製造方法は、蒸発乾固手段によりＨＣ吸着剤粉末の表面に薄く触媒金属（この場合はＰｄ）が担持された触媒金属担持ＨＣ吸着剤粉末を、触媒担体にウオッシュコートする方法であるから、ＨＣが脱離して放出される時、ＨＣ吸着剤粉末表面の触媒金属で放出ＨＣを燃焼除去して、ＨＣ浄化率の充分な向上を図ることができる効果がある。また上述のウオッシュコート済みのハニカム担体に対してセリウムを含浸担持させたので、ＣｅＯ２（酸化セリウム）からのＯ２（酸素）の供給により、酸化反応にてＨＣを燃焼除去することができ、ＨＣ浄化率のより一層充分な向上を図ることができる効果がある。
【００１８】
上述の実施例により製造されたハニカムは、ＨＣ吸着剤によるＨＣ吸着能力と、ＣｅＯ２（酸化セリウム）による酸素吸蔵能力とを有し、かつ吸着ＨＣを触媒金属により円滑に酸素と反応させて浄化することができる。
【００１９】
上述の図４に示す実施例の製造方法により製造された複合触媒（ハニカム）を、Ｖ型６気筒２５００ｃｃエンジンのアンダフロア位置に搭載し、ＣＶＳ４モード（米国標準走行モードのＦＴＰモードと同意）のＹ１モードにて実車走行し、触媒コンバータ前後のＨＣ量を測定した後に、ＨＣ浄化率を算出した結果を次の［表１］に実施例１として示す。なお、この実車走行テストは図１に示すキャタリストケース６内に複合触媒のみを配置し、コンバータ容量を１．３リッタに設定した場合のデータである。また比較例１、比較例２は通常の三元触媒を備えた触媒コンバータに対して上述同様の実車走行テストを行なった結果を示す。
【００２０】
【表１】

Figure 0003596026
上記の［表１］から明らかなように、実施例１は比較例１，２に対して優れたＨＣ浄化率を示す。すなわち上記実施例１の複合触媒は冷間時における排気ガス中のＨＣをＨＣ吸着剤で一旦吸着し、暖機後においてＨＣ吸着剤から脱離して放出されるＨＣを触媒金属と接触しやすい構造としたことにより、ＨＣを燃焼浄化することができるので、上表１の如く優れたＨＣ浄化率の達成を図ることができる。
【００２１】
この発明の構成と、上述の実施例との対応において、
この発明の排気ガス浄化用触媒は、実施例の複合触媒１０に対応し、
以下同様に、
触媒担体は、ハニカム担体１２に対応し、
ＨＣ吸着剤粉末が分散配置された層は、第１コート層１３に対応し、
触媒金属が分散配置された層は、第２コート層１４に対応し、
ＨＣ吸着剤は、ＭＯＲ（モルデナイト）に対応し、
触媒金属は、Ｐｄ（パラジウム）に対応するも、
この発明は、上述の実施例の構造のみに限定されるものではない。
【００２２】
例えば、ＨＣ吸着剤としては、上記要素の他に、ＭＦＩ（ゼオライト）、Ｈ型ＦＡＵ（Ｙ型ゼオライト）ＦＥＲ（フェリエライト）またはＣＨＡ（シャバサイト）を用いてもよく、触媒金属としてはＰｄ（パラジウム）の他にＰｔ−Ｒｈ（白金・ロジウム）やＰｄ−Ｒｈ（パラジウム・ロジウム）を用いてもよい。
【図面の簡単な説明】
【図１】本発明のエンジンの排気ガス浄化用触媒を備えた排気ガス浄化装置の断面図。
【図２】図１の複合触媒を抽出して示す斜視図。
【図３】図２の要部拡大断面図。
【図４】エンジンの排気ガス浄化用触媒の製造方法の実施例を示す工程図。
【図５】従来の排気ガス浄化用触媒の要部拡大断面図。
【符号の説明】
１０…複合触媒
１２…ハニカム担体（触媒成分担持用担体）
１３…第１コート層
１４…第２コート層[0001]
[Industrial applications]
The present invention makes a three-way catalyst (TWC) carry an HC adsorbent to remove HC (hydrocarbon), CO (carbon monoxide), and NOx (nitrogen oxide) harmful gases discharged from an exhaust port of an engine. The present invention relates to a method for producing an exhaust gas purifying catalyst for an engine that purifies the engine.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a catalyst for purifying exhaust gas of an engine, for example, there is a catalyst described in JP-A-3-202154.
That is, as shown in FIG. 5, a Pt-Rh-based catalyst component is formed on the surface of a honeycomb-shaped catalyst component-supporting carrier 101 (a so-called honeycomb carrier) such as cordierite (chemical symbol: Mg 2 Al 4 Si 5 O 18 ). A first coat layer 102 made of an alumina layer (specifically, a γ-Al 2 O 3 layer) containing (a platinum-rhodium-based catalyst component) is provided. On the first coat layer 102, CeO 2 (cerium oxide) and An exhaust gas purifying catalyst 104 provided with a second coat layer 103 containing an HC adsorbent that adsorbs unburned gas components of the engine.
[0003]
According to the conventional exhaust gas purifying catalyst 104, when the exhaust gas flows through the many pores 105 of the honeycomb carrier 101, when the exhaust gas is at a low temperature, HC (Hydrocarbon, hydrocarbon) in the exhaust gas is secondarily discharged. When adsorbed by the HC adsorbent in the second coat layer 103 and the exhaust gas temperature rises, HC is desorbed from the HC adsorbent and diffused and purified into the first coat layer 102 to increase the purification rate. On the other hand, since the first coat layer 102 of the Pt-Rh-based catalyst metal is formed inside the second coat layer 103 containing the HC adsorbent, there is sufficient contact between the desorbed HC and the catalyst metal. Therefore, there was a problem that it was not possible to obtain a good HC purification rate.
[0004]
[Problems to be solved by the invention]
The present invention has a structure in which HC released from an HC adsorbent that adsorbs HC and released is easily brought into contact with a catalyst metal, thereby achieving a sufficient improvement in HC purification rate. The catalyst adsorbent powder carrying the catalyst metal on which the catalyst metal is thinly disposed on the surface of the powder is wash-coated on the carrier for supporting the catalyst component. the release HC with metal removed by burning, it is possible to sufficiently improve the HC purification rate, further impregnated with an aqueous solution containing cerium in the layer of the washcoat, O from CeO 2 (cerium oxide) by firing ( 2 ) An object of the present invention is to provide a method for producing an exhaust gas purifying catalyst for an engine, in which HC is burned and removed by an oxidation reaction by supplying (oxygen) to further improve the HC purification rate.
[0005]
[Means for Solving the Problems]
In the method for producing an exhaust gas purifying catalyst for an engine according to the present invention, the HC adsorbent powder for adsorbing HC is dispersed and disposed on the surface of the catalyst component-carrying carrier, and the unpurified HC adsorbent is provided at least outside the HC adsorbent powder. A method for producing an exhaust gas purifying catalyst for an engine in which catalyst metals for purifying exhaust gas components are dispersed and arranged, comprising an HC adsorbent powder for adsorbing HC and a catalyst metal for purifying unpurified exhaust gas components. After mixing with the solution, the mixture is evaporated to dryness, the catalyst metal is supported on the surface of the HC adsorbent powder, and the HC metal adsorbent powder supporting the catalyst metal is formed. Is wash-coated on the surface of a carrier for supporting a catalyst component, and the wash coat layer is impregnated with an aqueous solution containing cerium and baked.
[0006]
【The invention's effect】
According to this invention, since the catalyst metal is dispersed and arranged at least outside the HC adsorbent powder, the HC desorbed and released from the HC adsorbent always comes into contact with the catalyst metal, so that the HC purification rate is reduced. There is an effect that sufficient improvement can be achieved. Moreover, the dryness constant, the catalytic metal-supported HC adsorbent powder thin catalytic metal is supported on the surface of the HC adsorbent powder, because it is a method of washcoat catalyst component carrying carrier, HC is desorbed release In this case, there is an effect that the released HC is burned and removed by the catalytic metal on the surface of the HC adsorbent powder, so that the HC purification rate can be sufficiently improved.
[0007]
Furthermore, since the washcoat layer is impregnated with an aqueous solution containing cerium and baked (it becomes cerium oxide by baking), oxidization is performed by supplying O 2 (oxygen) from CeO 2 (cerium oxide). There is an effect that the HC can be burned and removed by the reaction to further improve the HC purification rate.
[0008]
【Example】
An embodiment of the present invention will be described below in detail with reference to the drawings.
The drawings show a method for producing an exhaust gas purifying catalyst for an engine. First, the configuration of an exhaust gas purifying apparatus will be described with reference to FIGS. In FIG. 1, an exhaust gas purifying device 1 provided in an exhaust system of an engine is disposed at an underfloor position of a vehicle, and the exhaust gas purifying device 1 includes joining flange portions 2 and 3 at both front and rear ends. The front end side of the catalyst case 6 is connected to the exhaust gas inlet 4 via the cone portion 5, and the rear end side of the catalyst case 6 is connected to the exhaust gas outlet 8 via the cone portion 7. Here, the above-mentioned exhaust gas inlet 4 is connected to an exhaust port of the engine via an exhaust passage, and the above-mentioned exhaust gas outlet 8 is connected to a muffler via an exhaust passage.
[0009]
A three-way catalyst 9 for purifying unpurified exhaust gas components is disposed at a stage upstream of the exhaust gas in the above-described catalyst case 6 and an HC adsorbent for adsorbing HC at a stage downstream of the exhaust gas. A three-way catalyst for purifying unpurified exhaust gas components, a composite catalyst 10 in which CeO 2 (cerium oxide) is composited, is provided.
[0010]
As shown in FIG. 2, the latter-stage composite catalyst 10 has a columnar outer diameter, a honeycomb shape in the axial direction, and a large number of pores 11. In addition, as shown in FIG. 3, the cross-sectional structure of the MFI (zeolite) powder that adsorbs HC on the surface of a cordierite (Mg 2 Al 4 Si 5 O 18 ) honeycomb carrier 12 (a carrier for supporting a catalyst component) Forming a first coat layer 13 containing an HC adsorbent powder made of, and forming a second coat layer 14 containing a catalytic metal such as Pd (palladium) on the outer surface of the first coat layer 13; Cerium is carried on the two-layer coated honeycomb of the first coating layer 13 and the second coating layer 14 by the impregnation means.
[0011]
As described above, since the catalyst metal (see the second coat layer 14) for purifying unpurified exhaust gas components is dispersed and arranged outside the HC adsorbent powder (see the first coat layer 13), the exhaust gas The HC contained therein is desorbed from the HC adsorbent after being trapped by the HC adsorbent. However, since the released HC always comes into contact with the catalyst metal layer (see the second coat layer 14), the HC purification rate is sufficiently high. There is an effect that can be improved.
[0012]
The method for producing the composite catalyst 10 shown in FIG. 3 will be described in detail with reference to the process chart shown in FIG.
First, in a first step S21 in FIG. 4, the HC adsorbent powder and an aqueous solution containing a catalytic metal (an aqueous solution is used in this embodiment, but an organic solution may be used instead of the aqueous solution) is mixed.
[0013]
That is, 200 g of hydrogen ion exchanged MOR (mordenite) powder (Caban ratio: 20) was used as the HC adsorbent, 120 g of palladium nitrate aqueous solution (Pd, 4.4 wt%) was used as the catalyst metal-containing aqueous solution, and both of them were 100 g of H 2. Mix and stir in O (water).
[0014]
Next, in the second step S22 of FIG. 4, when the stirring is continued while heating the aqueous solution using, for example, a hot plate as a heating means, a dry powder in which Pd (palladium) is supported on the HC adsorbent powder is obtained. be able to. This method is generally called evaporation to dryness.
[0015]
Next, in the third step S23 in FIG. 4, the above-mentioned catalyst metal-supported HC adsorbent powder is wash-coated on the honeycomb carrier. That is, the catalyst metal-supported HC adsorbent powder obtained by the above-mentioned evaporation to dryness means and hydrated alumina as a binder are mixed with water at a weight ratio of 5: 1 to form a slurry, The honeycomb carrier is immersed in the slurry, pulled up, air-blasted, and dried repeatedly to wash coat the Pd-supported MOR on the honeycomb carrier and then fired. In addition, the total carrying amount was 200 g / liter.
[0016]
Next, in a fourth step S24 in FIG. 4, the above-mentioned wash-coated honeycomb carrier is impregnated with cerium. That is, 164 g of Ce (NO 3 ) 3 (cerium nitrate) is dissolved in one liter of water, and the honeycomb carrier is impregnated with the cerium nitrate aqueous solution. Then, in the fifth step S25 of FIG. The honeycomb support impregnated with the aqueous solution of NO 3 ) 3 (cerium nitrate) was calcined to produce a composite catalyst having 50 g / liter of CeO 2 (cerium oxide) supported thereon.
[0017]
As described above, the method for manufacturing the exhaust gas purifying catalyst of the engine according to the above embodiment is characterized in that the catalyst metal (in this case, Pd) is thinly supported on the surface of the HC adsorbent powder by evaporation to dryness. In this method, the catalyst powder is wash-coated on the catalyst carrier. When HC is desorbed and released, the released HC is burned and removed by the catalyst metal on the surface of the HC adsorbent powder, and the HC purification rate is sufficiently improved. There is an effect that can be achieved. Since cerium against above wash-coated honeycomb carrier was impregnated carrier, the supply of O 2 (oxygen) from CeO 2 (cerium oxide), Ki out burning off the HC by the oxidation reaction Thus, there is an effect that the HC purification rate can be more sufficiently improved.
[0018]
The honeycomb manufactured according to the above-described embodiment has the ability to adsorb HC using an HC adsorbent and the ability to occlude oxygen using CeO 2 (cerium oxide), and purifies the adsorbed HC by smoothly reacting the adsorbed HC with oxygen using a catalytic metal. can do.
[0019]
The composite catalyst (honeycomb) manufactured by the manufacturing method of the embodiment shown in FIG. 4 described above is mounted on the underfloor position of a V-type 6-cylinder 2500cc engine, and is operated in a CVS4 mode (same as the FTP mode in the US standard driving mode). After running the actual vehicle in the Y1 mode and measuring the amount of HC before and after the catalytic converter, the result of calculating the HC purification rate is shown as Example 1 in the following [Table 1]. The actual vehicle running test is data when only the composite catalyst is arranged in the catalyst case 6 shown in FIG. 1 and the converter capacity is set to 1.3 liters. Comparative Examples 1 and 2 show the results of performing the same vehicle running test as described above on a catalytic converter having a normal three-way catalyst.
[0020]
[Table 1]
Figure 0003596026
As is clear from the above [Table 1], Example 1 shows an excellent HC purification rate with respect to Comparative Examples 1 and 2. That is, the composite catalyst of Example 1 has a structure in which HC in the exhaust gas at the time of cold is once adsorbed by the HC adsorbent, and the HC released and released from the HC adsorbent after the warm-up is easily in contact with the catalyst metal. As a result, HC can be purified by combustion, so that an excellent HC purification rate can be achieved as shown in Table 1 above.
[0021]
In correspondence between the configuration of the present invention and the above-described embodiment,
The exhaust gas purifying catalyst of the present invention corresponds to the composite catalyst 10 of the embodiment,
Similarly,
The catalyst carrier corresponds to the honeycomb carrier 12,
The layer in which the HC adsorbent powder is dispersed corresponds to the first coat layer 13,
The layer in which the catalyst metal is dispersed corresponds to the second coat layer 14,
HC adsorbent corresponds to MOR (mordenite),
The catalyst metal corresponds to Pd (palladium),
The present invention is not limited only to the structure of the above embodiment.
[0022]
For example, as the HC adsorbent, MFI (zeolite), H-type FAU (Y-type zeolite) FER (ferrierite), or CHA (chabazite) may be used in addition to the above-described elements, and Pd ( Pt-Rh (platinum-rhodium) or Pd-Rh (palladium-rhodium) may be used in addition to palladium).
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an exhaust gas purifying apparatus provided with an exhaust gas purifying catalyst for an engine of the present invention.
FIG. 2 is a perspective view showing an extracted composite catalyst of FIG. 1;
FIG. 3 is an enlarged sectional view of a main part of FIG. 2;
FIG. 4 is a process diagram showing an embodiment of a method for producing an exhaust gas purifying catalyst for an engine.
FIG. 5 is an enlarged sectional view of a main part of a conventional exhaust gas purifying catalyst.
[Explanation of symbols]
10: Composite catalyst 12: Honeycomb carrier (carrier for supporting catalyst component)
13: first coat layer 14: second coat layer

Claims (1)

触媒成分担持用担体の表面にＨＣを吸着するＨＣ吸着剤粉末が分散して配置され、
上記ＨＣ吸着剤粉末の少なくとも外側に未浄化の排気ガス成分を浄化する触媒金属が分散配置された
エンジンの排気ガス浄化用触媒の製造方法であって、
ＨＣを吸着するＨＣ吸着剤粉末と、未浄化の排気ガス成分を浄化する触媒金属を含む溶液とを混合した後、蒸発乾固して上記ＨＣ吸着剤粉末の表面に上記触媒金属を担持して、触媒金属を担持したＨＣ吸着剤粉末を形成した後に、触媒金属担持ＨＣ吸着剤粉末を触媒成分担持用担体の表面にウオッシュコートし、さらに該ウオッシュコートの層にセリウムを含む水溶液を含浸し、焼成した
エンジンの排気ガス浄化用触媒の製造方法。HC adsorbent powder for adsorbing HC is dispersed and arranged on the surface of the catalyst component supporting carrier,
A method for manufacturing an exhaust gas purifying catalyst for an engine, wherein a catalyst metal for purifying unpurified exhaust gas components is dispersed and arranged at least outside the HC adsorbent powder,
After mixing an HC adsorbent powder for adsorbing HC and a solution containing a catalyst metal for purifying unpurified exhaust gas components, the mixture is evaporated to dryness to carry the catalyst metal on the surface of the HC adsorbent powder. After forming the HC adsorbent powder supporting the catalyst metal, wash-coat the catalyst metal-supported HC adsorbent powder on the surface of the catalyst component-supporting carrier, and further impregnated the washcoat layer with an aqueous solution containing cerium, A method for producing a fired catalyst for purifying exhaust gas of an engine.
JP8790994A 1993-10-09 1994-03-31 Method for producing catalyst for purifying exhaust gas of engine Expired - Fee Related JP3596026B2 (en)

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JP2002045702A (en) * 2000-08-08 2002-02-12 Cataler Corp Catalyst for purifying exhaust gas
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